1. Field of the Invention
The present invention relates generally to a system for controlling ignition in an internal combustion engine, and more particularly, to a system configured to produce repetitive spark for ignition having termination based on the feedback information concerning the state of combustion.
2. Description of the Related Art
There has been much investigation in the ignition art directed to systems for generating multiple spark events during combustion. Such systems are sometimes referred to as xe2x80x9cmultichargexe2x80x9d systems. Such ignition systems provide a succession of spark breakdowns to ensure ignition of a combustible air/fuel mixture introduced into a cylinder of an internal combustion engine, as seen by reference to U.S. Pat. No. 5,014,676 issued to Boyer. Boyer discloses a system configured to provide a series of sparks to increase the number of ignition events and hence the probability of combustion of the air/fuel mixture by extending the time and total energy available for combustion. Boyer discloses an ignition coil that undergoes an initial charge (i.e., initial dwell) wherein a primary current is established in a primary winding of the ignition coil. The initial dwell is immediately followed by an initial discharge of the ignition coil wherein a secondary current in a secondary winding thereof discharges through a spark plug to generate a first spark. Subsequent recharge intervals (i.e., subsequent dwell periods) follow, accompanied by respective discharge intervals (i.e., spark events). The number of sparks produced is generally determined by a predetermined operating strategy (e.g., a fixed number of sparks, or, the greatest number of sparks that can be initiated before the end of a predetermined angle of engine rotation). However, prior approaches such as the system disclosed in Boyer have shortcomings.
One shortcoming involves unnecessary spark plug wear due to added spark events after combustion has already commenced. Another shortcoming involves the unnecessary delivery of energy to the combustion chamber at certain operating conditions (e.g., via additional sparks when combustion has already commenced via earlier sparks). Reservations arising from these shortcomings have, to some extent, impeded acceptance of multicharge ignition systems, which have many advantages, such as enhanced initiation of combustion, especially under less than ideal combustion conditions.
It is also known to provide a system for determining a combustion condition in an internal combustion engine, as seen by reference to U.S. Pat. No. 5,866,808 to Ooyabu et al. Ooyabu et al. disclose an apparatus for detecting a level of combustion by sensing an ion current level.
There is therefore a need to provide an ignition control system for producing repetitive spark in a combustion chamber of an internal combustion engine that minimizes or eliminates one or more of the shortcomings as set forth above.
An ignition system in accordance with the present invention is characterized by the features specified in claim 1.
One object of the present invention is to provide an ignition system suitable for use in generating repetitive spark that minimizes or eliminates the number of unnecessary spark events to reduce spark plug wear.
It is another object of the present invention to deliver only the amount of energy necessary to start combustion.
These and other objects, advantages, and features of the present invention are realized by an ignition system in accordance with the present invention. One advantage of the present invention is that multicharge operation (i.e., repetitive spark during the firing of one cylinder) is terminated when combustion has commenced and has proceeded to a predefined level, as determined by a combustion detection circuit. This termination feature eliminates unnecessary spark events, thereby reducing spark plug wear. In addition, since multicharge operation is terminated when combustion is detected, there is no unnecessary delivery of energy to the combustion chamber beyond that required for initiating combustion of an air/fuel mixture introduced into the chamber.
An ignition system in accordance with the present invention is configured for use with an internal combustion engine. The ignition system includes an ignition coil having a primary winding and a secondary winding that is coupled to a spark plug in a combustion chamber of the engine. The system further includes a switch responsive to an ignition control signal for causing a primary current to flow through the primary winding circuit. The system also includes a control circuit, which is configured to generate the ignition control signal so as to produce a plurality of sparks at the spark plug during a combustion event in the cylinder. The ignition system further includes a combustion detection circuit that is disposed in sensing relation with the combustion cylinder. The combustion detection circuit is configured to generate a combustion detect signal when combustion has begun and has proceeded to a preselected level. Advantageously, the control circuit is further configured to terminate the ignition control signal to avoid further spark events in response to the combustion detect signal.
Other objects, features, and advantages of the present invention will become apparent to one skilled in the art from the following detailed description and accompanying drawings illustrating features of this invention by way of example, but not by way of limitation.